Strainer for digesters



April 7, 1953 Filed May 19, 1948 l.. c. NEVIN 2,634,209

STRAINER FOR DIGESTERS 5 Sheets-Sheet l April 7, 1953 c. NEvlN STRAINER FOR DIGESTERS 5 Sheets-Sheet 2 Filed May 19, 194

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April 7, 1953 I l.. c. NEvlN STRAINER FOR DIGESTERS 5 Sheets-Sheet 5 Filed May 19, 1948 UGGOCQOOOGOOGGOGG OOOOGOGOOOOOOOGO.

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OOGGOO-G .OGOOGGOGG GOOOOOOOOOOGOOQO @GGGOG Patented Apr. 7, 1953 STRAINER. FOR DIGES'IERS Leonard Charles Nevin, Watertown, N. Y., as-

signor to Chemipulp Process, Inc., Watertown,

Application May 19, 1948, lSerial N o. 27,882

8 Claims.

This invention relates to improvements Vin strainers and more particularly to strainers of the type used in tanks or the like to prevent solids or semi-solids from discharging through a suction line with the liquid employed in the treatment of such solids or semi-solids. More specically, the invention pertains to the strainers employed in digester circulating systems, to allow the withdrawal of the digester cooking liquor through a suction nozzle while withholding all the chips ,and pulp within the digester, as such solids or semi-solids would clog the pump used to circulate the liquor as well as the pipe lines and valves forming parts of the conventional digester circulating system.

One of the objects of the invention is to provide a strainer comprising a multiplicity of plates which may be interlocked with one another in such manner as to stiifen the strainer at the lines where the plates are interlocked.

Another object is to provide strainer plate units thin enough to be flexible and so mounted within the digester that under varying conditions within the digester, the plates may move inwardly and outwardly sufficiently to prevent formation of scale or lime deposits which, in known strainers, eventually plug the holes or perforations of the strainer plates.

A still further obj ect is to supply strainer plates or sections light enough to be easily handled by one man so that the plates may be readily in- *y stalled in or removed from the digester.

A further object is the provision of strainer plates or sections which may be readily renewed so that a mill need carry only a very few of the plates or units for renewal in case of failure of any kind.

Another object is to provide novel means for connecting the plates to the digester and to one another.

With the foregoing objects outlined and with other objects in View which will appear as the description proceeds, the invention consists in the novel features hereinafter described in detail, illustrated in the accompanying drawings, and more particularly pointed out ,in-the appended claims. A

In the drawings:

' Fig. 1 is a side elevation of a digester with a conventional suction line, branch line and nozzles, and with a portion of the digesterl shown in diametrical Vertical section to illustrate generally the arrangement of my improvements.

Fig. 2 is a horizontal sectional view taken on the line 2-2, of Fig. 1. l

. Fig. 3 is, an enlarger vertical sectional view of adetailtaken onthe line 3- -310f Fig, 2.

' Fig. 4 is a similar view taken on the line 4-4 of Fig. 2.

Fig. 5 is an enlarged horizontal sectional view of a detail taken on the line 5 5 of Fig. 1.

Fig. 6 is a top plan view of one of the strainer plates or units.

Fig. 7 is a side elevational View of such plate or unit.

Fig. 8 is an enlarged vertical sectional view taken on the line 8 8 of Fig. 2.

Fig. 9 is an enlarged vertical sectional view, partly in elevation, and illustrating the means for retaining or supporting one of the strainer plates at the lower edge of the latter.

Fig. 10 is an enlarged view of a detail illustrating means whereby adjacent strainer plate retaining straps may be secured in place.

Fig. 11 is a similar View of means for retaining a strap in place between the ends thereof.

Fig. 12 is a fragmentary elevation of the strainer viewed from within the digester at the place where the suction outlet nozzle is located.

Referring more specifically to the drawings, it will be noted that Fig. 1 shows a digester I3 having a metallic shell i4 lined with a brick liner l5 or the like, that is not aiected by the liquor employed in the cooking of wood chips within the digester. While I will describe the invention in connection with a digester, it will be obvious to those familiar with strainers of the` type disclosed that such a strainer may be used in any tank or container from which liquid is to be discharged without releasing the solids, or semi-solids within the container.

In accordance with the present invention, the liner is preferably corbelled as indicated at I6 in Fig. 1, and the corbelled portion of the liner is provided with two grooves Il and I8, one arranged above the other, with one of the grooves, l1, extending entirely around the liner and with the other, I8, extending only Both grooves communicate at the suction nozzle i9 as illustrated in Fig. 3.

In keeping with the invention, a semi-circular screen 20 obstructs the mouth of the groove I8 while the mouth of the groove I1 is obstructed by a semi-circular screen 2l combined with a semicircular imperforate member 22. At this point, it will be noted that the screen 20 extends for 180 adjacent the nozzle i9 and the latter is arranged midway between the ends of such screen, while the screen 2| extends for 180 at the side of the digester diametrically opposite the place where the nozzle I9 is positioned. This arrangement assures equal distribution of the cooking liquor through the screens or collector ring and results in a much higher yield of p ulp and a more uniform pulp than if a single screen or collector ring perforated throughout its entire circumference were employed with one suction nozzle.

Referring now to the details of the strainer, it will be observed that the parts thereof may be mounted at the interior of the liner by any suitable means, permitting ready installation or removal, but I preferably weld anchor elements 23 to the interior of the shell so as to eliminate any additional openings therethrough. Each of these elements may consist of a nut to which a rod 24 is connected by threads, to facilitate in stallation or removal of any rod. Each rod extends radially within the digester and is provided at its inner end (Figs. 9, and 11) with a head 25 having a vertically disposed slot 26 for the reception of a wedge 21. Each wedge is preferably inserted into the slot from below the rod, and is then secured in position by means of a removable pin 28. Of course, the rods extend through the liner and at the inner surface thereof, arrange backing rings 29 supported by the rods 24. Each ring 29 may be made in a single piece or of segmental form, as will be obvious. At the inner side of the backing rings, I arrange on the rods, spacer rings 30 which may also be of integral construction or be constituted by segments, and between the spacers 3U and the wedges 21, I arrange retainer rings 3l. As it will be desirable at times to remove one or more of the plates 32, making up the strainers, without disturbing other plates, the retainer ring 3| may be of segmental construction as indicated at 3A in Fig. 10, so that the adjacent ends of two segments may be secured in position by a bridge plate held in position by one of the wedges 21. As indicated in Fig. 11, an intermediate portion 36 of a retainer plate may be secured in place by any one of the wedges 21.

Referring now to the plates constituting the collector ring or strainer members, it will be noted in Fig. 9 that the thickness of each plate 32 is less than the thickness of the spacer 39. Hence, each strainer plate is free to move inwardly and outwardly to a certain degree so as to prevent the formation of scale, and the like on the perforated plates.

As best shown in Figs. 6 and '1, each plate 32 comprises a planar body 38 having a vertical flange 39 at one side edge and a vertical hook 40 at the opposite side edge. When a strainer plate is detached from the digester, the flange 39 inclines or converges toward the hook 40, but when the flange extends into the cavity 4| of the hook, it may flex and assume a position substantially parallel to the shank of the hook, asindicated at i2 in Fig. 5. At this point, it will be noted, as in Fig. l2, that the plates forming the screens 20 and 2| are perforated at `1&3 while the plates forming the portion 22 of the strainer are imperforate, as indicated at 44 in Fig. l2.

The strainer preferably includes, at the point where the suction nozzle is located, an imperiorate obstruction plate or door i5 which may be interlocked with the adjacent plates of the strainer by the flange and hook joints, as shown at 46. The door structure 45 is retained in position by upper and lower straps 111 and -48 and held in place by some of the wedges 21.

The collector ring or strainer, including all its parts except the nuts 23 are preferably of acid resisting chrome nickel steel, Any acid resisting material equal to or better than chrome nickel steel would be satisfactory.

The interlocking joints 42, 46 not only serve the purpose of holding the plates together to prevent fiber from passing between them, but also act as stiffeners to add strength to withstand pressure conditions within the digester. As each plate is thin enough to flex under pressure and the plates can move in and out, any scale deposits such as sulphates or lime that may be formed will be loosened during the operation of the digester. This makes this type of construction selfcleaning and the perforations do not have to be rebored on account of deposition of scale deposits.

As will be apparent from the drawings, the various plate retaining straps and wedges may b'e made light enough so that they can be easily handled by one man and as practically all of the plates are of the same dimensions throughout the whole of the strainer, it is evident that a mill need carry only a very few of these plate sections or units to take care of renewal in case of failure of any kind.

I believe that my strainer is much less expensive than others previously used and I know that it operates clean, that is, it does not hold up stock in the digester, as is the case with strainers of known types.

In recapitulation, my strainer is much less expensive to build than others. It is self-cleansing, it is held in place in such a way as to allow expansion to prevent temperature strains, the main parts are interlocked, and the interlocks serve as stiffeners to strengthen the plates.

While I have disclosed what I now consider to be some preferred embodiments of my invention in such manner that the same may be readily understood by those skilled in the art, I am aware that changes may be made in the details disclosed without departing from the spirit of the invention, as expressed in the following claims.

What I claim and desire to secure by Letters Patent is:

l. In a fibrous pulp digester, a tank having a metallic shell, a liner covering the inner surface of said shell, said liner being provided with a groove extending circumferentially of the tank, nuts rigidly secured to the inner surface of the shell arranged above and below the groove, rods having threaded connection with the nuts and extending through the liner above and below the groove, spacers arranged on the rods at the inner side of the liner, a horizontally disposed row of plates arranged between said spacers and covering said groove, each plate being of less thickness than the thickness of the spacers, retaining straps mounted on the rods limiting movement of said plates away from the shell, means detachably connecting the retaining straps to said rods, one of said plates having an inwardly extending vertical flange at one side edge, and a vertically disposed hook carried by an opposite side of an adjacent plate interlocked with said flange.

2. In a brous pulp digester, a tank having a metallic outer shell, a non-metallic liner of acid resisting material covering the inner surface of said shell, said liner being provided with a groove extending circumferentially of the tank, nuts rigidly secured to the inner surface of the shell arranged above and below thegroove, rods having threaded connection with the nuts extending through the liner above and below the groove, a metallic member supported by the rods along the inner surface of the liner, a'spacer member on each rod at the inner side of the metallic member. a retaining member on said bolts, a horigroove and arranged between said metallic member and the retaining member, each plate being of less thickness than the thickness of the spacer members, removable means carried by the rodslimiting movement to said retaining member away from the shell, an inwardly extending vertical flange at one side edge of each plate, and a vertically disposed hook at the opposite side of each plate interlocked with said flange.

3. In a fibrous pulp digester, a tank having a shell, a liner covering an inner surface of said shell, said linerhaving a groove therein extending circumferentially of the tank, anchor members carried by the shell extending radially inward beyond an inner surface of the liner and at opposite sides of the groove, retaining members detachably mounted on said anchor members maintained in spaced relationship inwardly of the inner surface of said liner, plates covering said groove arranged with edge portions between the liner and said retaining members, each plate adjacent the retaining members having a thickness less than the radial dimensions of the space between the liner and the retaining members whereby the plates may move towards and away from the liner to a limited extent, and means at the ends of the plates connecting one plate to an adjacent plate. v

4. In ai'lbrous pulp digester, a tank having a shell, a liner covering the inner surface of the shell, said liner having a groove therein extending circumferentially of the tank, anchor members carried by the shell extending radially inward beyond an inner surface of the liner at opposite sides of the groove, a spacer element on each anchor member at the inner surface of the liner, strainer plates covering said groove arranged between the spacer elements, retaining members removably mounted on said anchor members and overlying edge portions oi. the strainer plates, each strainer plate adjacent the retaining members being of less thickness than the radial dimensions of said spacer elements so that; the strainer4 plates may move towards and away from the liner to a limited extent to remove solids from the strainer plates, and means connecting adjacent ends of the strainer plates to each other.

5. In a fibrous pulp digester, a shell, a liner forming an inner wall of the digester, said liner `having a circumferential extending groove therein, a, plurality of plates covering said groove, a flange projecting from one end of each plate radially inwardly of the digester, a hook carried `by the opposite end of each plate including a shank portion extending radially inward of the digester and an arcuate end portion embracing and overlying an end of the ilange of an adjacent plate to prevent fibers and chips from moving between adjacent ends of the plates, retaining straps overlying opposite edge portions of said plates, means maintaining said retaining straps in spaced relation from an inner-surface of the liner whereby the plates may move radially inwardly'and outwardly with respect to the shell as limited by the retaining straps and the liner `to shake solids from the plates, and means detachably securing the retaining straps to the shell.

6. In a fibrous pulp digester, a liner forming an inner wall thereof, said liner having a circumferentially extending groove therein, a plurality of .apertured plates covering said groove, a

` flange of an adjacent plate to provide a connection therebetween, means maintaining the apertured plates in positions covering said groove, and

said retaining means being spaced from the liner to permit limited movement of the plates towards and away from the liner to shake solids therefrom and prevent obstruction of the apertures in the plates.

7. Ina fibrous pulp digester, a liner forming an inner wall of the digester, said liner having a circumferentially extending groove therein, a plurality of flexible strainer plates covering said groove, a flange projecting from one end of each strainer plate radially inwardly of the digester, a hook carried by the opposite end of each strainer plate including a shank portion extending radially inwardly of the digester having an arcuate end portion embracing an inner end of the flange of an adjacent strainer plate to prevent fibers and chips from moving between adjacent plates, retaining straps overlying opposite edge portions of said strainer plates maintaining them in positions covering the groove, and means detachably securing the retaining straps to the digester.

8. An element for the strainer of a iibrous pulp digester comprising, a flexible metal plate having a rectangular shaped body portion normally arranged in a single plane and adapted to assume an arcuate shape and lie along the inner wall of the digester, a flange carried by one end of the plate member projecting from the body portion ai; an angle less than ninety degrees when the body portion is in said single plane, a hook carried by the opposite end of the body portion including a shank extending substantially at right angles with respect to the body portion when it is in said single plane, and a curved portion carried by an end of the shank terminating in an end tip substantially parallel with the shank and spaced therefrom a distance greater than the thickness of said flange.

LEONARD CHARLES NEVI'N.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 401,610 Tompkins Apr. 16, 1889 478,365 Rerrich July 5, 1892 885,786 Prinz Apr. 28, 1908 1,051,530 Whalen Jan. 28, 1913 1,625,373 Panzl Apr. 19, 1927 1,777,217 Morterud Sept. 30, 1930 1,943,221 Kruger Jan. 9, 1934 2,062,127 Guettler Nov. 24, 1936 2,064,901 Fletcher Dec. 22, 1936 2,163,437 Richmond June 20, 1939 2,463,814 Skinner Mar. 8, 1949 FOREIGN PATENTS Number Country Date 44,414 [Norway Sept. 26, 1927 141,496 Germany Apr. 25, 1935 97,871 Sweden Jan. 23, 1940 100,091 Sweden Oct. 25, 1940 

1. IN A FIBROUS PULP DIGESTER, A TANK HAVING A METALLIC SHELL, A LINER COVERING THE INNER SURFACE OF SAID SHELL, SAID LINER BEING PROVIDED WITH A GROOVE EXTENDING CIRCUMFERENTIALLY OF THE TANK, NUTS RIGIDLY SECURED TO THE INNER SURFACE OF THE SHELL ARRANGED ABOVE AND BELOW THE GROOVE, RODS HAVING THREADED CONNECTION WITH THE NUTS AND EXTENDING THROUGH THE LINER ABOVE AND BELOW THE GROOVE, SPACERS ARRANGED ON THE RODS AT THE INNER SIDE OF THE LINER, A HORIZONTALLY DISPOSED ROW OF PLATES ARRANGED BETWEEN SAID SPACERS AND COVERING SAID GROOVE, EACH PLATE BEING OF LESS THICKNESS THAN THE THICKNESS OF THE SPACERS RETAINING STRAPS MOUNTED ON THE RODS LIMITING MOVEMENT OF SAID PLATES AWAY FROM THE SHELL, MEANS DETACHABLY CONNECTING THE RETAINING STRAPS TO SAID RODS, ONE OF SAID PLATES HAVING AN INWARDLY EXTENDING VERTICAL FLANGE AT ONE SIDE EDGE, AND A VERTICALLY 